Modern portable devices, such as laptops, tablets, smartphones, smart watches, gaming devices and other consumer electronics, are designed to run system and user space applications when the devices are held by or in contact with users. Thermal management for these devices regulates not only the internal temperature of the device to ensure safe operation, but also the surface temperature of the device such that it is comfortable for the user to touch the device. Thermal management prevents the device from generating excessive heat, as excess temperature can degrade the performance, life, and reliability of the device. One form of dynamic thermal management is thermal throttling. Thermal throttling reduces the processor performance when the processors in the device are heavily loaded, to thereby limit the internal temperature and the surface temperature to acceptable levels.
One approach to estimating the surface temperature of a portable device is to use the internal temperature minus a fixed offset to calculate the surface temperature. However, the difference (i.e., offset) between the internal temperature and the surface temperature can vary from one device product to another, and can vary in the same device under different usage scenarios and different levels of power consumption. Using such an oversimplified approach often leads to inaccurate estimation of the surface temperature, and may cause performance to be throttled before the surface temperature reaches a predetermined limit.
Another approach to estimating the surface temperature of a portable device is to place a temperature sensor at the device surface; e.g., the display. However, such a sensor detects the temperature of a limited surface area on the device. In some usage scenarios there may be multiple heat sources located in different parts of the device, causing non-uniform temperature rise on the device surface. Furthermore, in different usage scenarios there may be different heat sources inside the device, causing the surface temperature to rise on different parts of the device surface. Thus, a temperature sensor at a fixed surface location may be unable to detect surface temperature change across these usage scenarios.
Thus, there is a need for improvement in surface temperature determination to thereby enable accurate dynamic thermal management of a portable device.